Follow-up PET/CT of alveolar echinococcosis: Comparison of metabolic activity and immunodiagnostic testing

PURPOSE To investigate the potential role of follow-up 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in therapy control of inoperable patients with alveolar echinococcosis. MATERIALS AND METHODS In this single-center retrospective cohort study, 48 PET/CT of 16 patients with confirmed alveolar echinococcosis were analysed. FDG-uptake of the most active echinococcosis manifestation was measured (i.e., maximum standardized uptake value (SUVmax) and in relation to background activity in normal liver tissue (SUVratio)) and compared to immunodiagnostic testing. For clinical patient follow-up, patient demographics, laboratory data, including E. granulosus hydatid fluid (EgHF) antibody units (AU) as well as clinical and treatment information were assessed for all patients at the time of PET/CT, and at the last recorded clinical visit. RESULTS Metabolic activity of PET/CT measured in the echinococcosis manifestation was significantly correlated with EgHF AU (p < 0.001). The differences in metabolic activity of echinococcosis manifestations between two consecutive PET/CT examinations of the same patient and differences in EgHF AU in the respective time intervals displayed a significant positive correlation (p = 0.01). A trend for a more rapid decline in SUVratio liver over time was found in patients who stopped benzimidazole therapy versus patients who did not stop therapy (p = 0.059). CONCLUSION In inoperable patients with alveolar echinococcosis, the course of metabolic activity in follow-up PET/CT is associated to the course EgHF antibody levels. Both parameters may potentially be used to evaluate the course of the disease and potentially predict the duration of benzimidazole therapy

Age- and Gender Dependent Liver Fat Content in a Healthy Normal BMI Population as Quantified by Fat-Water Separating DIXON MR Imaging

OBJECTIVES To establish age- and sex-dependent values of magnetic resonance (MR) liver fat-signal fraction (FSF) in healthy volunteers with normal body-mass index (BMI). METHODS 2-point mDIXON sequences (repetition time/echo time, 4.2msec/1.2msec, 3.1msec) at 3.0 Tesla MR were acquired in 80 healthy volunteers with normal BMI (18.2 to 25.7 kg/m2) between 20 and 62 years (10 men/10 women per decade). FSF was measured in 5 liver segments (segment II, III, VI, VII, VIII) based on mean signal intensities in regions of interest placed on mDIXON-based water and fat images. Multivariate general linear models were used to test for significant differences between BMI-corrected FSF among age subgroups. Pearson and Spearman correlations between FSF and several body measures were calculated. RESULTS Mean FSF (%) ± standard deviations significantly differed between women (3.91 ± 1.10) and men (4.69 ± 1.38) and varied with age for women/men (p-value: 0.002/0.027): 3.05 ± 0.49/3.74 ± 0.60 (age group 20-29), 3.75 ± 0.66/4.99 ± 1.30 (30-39), 4.76 ± 1.16/5.25 ± 1.97 (40-49) and 4.09 ± 1.26/4.79 ± 0.93 (50-62). FSF differences among age subgroups were significant for women only (p = 0.003). CONCLUSIONS MR-based liver fat content is higher in men and peaks in the fifth decade for both genders

Prediction of benzimidazole therapy duration with PET/CT in inoperable patients with alveolar echinococcosis

Alveolar echinococcosis is a rare parasitic disease, most frequently affecting the liver, as a slow-growing tumor-like lesion. If inoperable, long-term benzimidazole therapy is required, which is associated with high healthcare costs and occasionally with increased morbidity. The aim of our study was to determine the role 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in staging of patients with alveolar echinococcosis and to identify quantitative imaging parameters related to patient outcome and/or duration of benzimidazole therapy. In this single-center retrospective cohort study, 47 PET/CT performed for staging in patients with confirmed alveolar echinococcosis were analysed. In 43 patients (91%) benzimidazole therapy was initiated and was successfully stopped after a median of 870 days (766-2517) in 14/43 patients (33%). In inoperable patients, tests for trend of survivor functions displayed clear trends for longer benzimidazole therapy duration (p = 0.05; n = 25), and for longer time intervals to reach non-detectable serum concentration of Em-18 antibodies (p = 0.01, n = 15) across tertiles of SUVratio (maximum standardized uptake value in the echinococcus manifestation compared to normal liver tissue). Hence, in inoperable patients with alveolar echinococcosis, PET/CT performed for staging may predict the duration of benzimidazole therapy

Individual participant data meta-analysis of LR-5 in LI-RADS version 2018 versus revised LI-RADS for hepatocellular carcinoma diagnosis

Background A simplification of the Liver Imaging Reporting and Data System (LI-RADS) version 2018 (v2018), revised LI-RADS (rLI-RADS), has been proposed for imaging-based diagnosis of hepatocellular carcinoma (HCC). Single-site data suggest that rLI-RADS category 5 (rLR-5) improves sensitivity while maintaining positive predictive value (PPV) of the LI-RADS v2018 category 5 (LR-5), which indicates definite HCC. Purpose To compare the diagnostic performance of LI-RADS v2018 and rLI-RADS in a multicenter data set of patients at risk for HCC by performing an individual patient data meta-analysis. Materials and Methods Multiple databases were searched for studies published from January 2014 to January 2022 that evaluated the diagnostic performance of any version of LI-RADS at CT or MRI for diagnosing HCC. An individual patient data meta-analysis method was applied to observations from the identified studies. Quality Assessment of Diagnostic Accuracy Studies version 2 was applied to determine study risk of bias. Observations were categorized according to major features and either LI-RADS v2018 or rLI-RADS assignments. Diagnostic accuracies of category 5 for each system were calculated using generalized linear mixed models and compared using the likelihood ratio test for sensitivity and the Wald test for PPV. Results Twenty-four studies, including 3840 patients and 4727 observations, were analyzed. The median observation size was 19 mm (IQR, 11–30 mm). rLR-5 showed higher sensitivity compared with LR-5 (70.6% [95% CI: 60.7, 78.9] vs 61.3% [95% CI: 45.9, 74.7]; P < .001), with similar PPV (90.7% vs 92.3%; P = .55). In studies with low risk of bias (n = 4; 1031 observations), rLR-5 also achieved a higher sensitivity than LR-5 (72.3% [95% CI: 63.9, 80.1] vs 66.9% [95% CI: 58.2, 74.5]; P = .02), with similar PPV (83.1% vs 88.7%; P = .47). Conclusion rLR-5 achieved a higher sensitivity for identifying HCC than LR-5 while maintaining a comparable PPV at 90% or more, matching the results presented in the original rLI-RADS study

Protocol requirements and diagnostic value of PET/MR imaging for liver metastasis detection

PURPOSE: To compare the accuracy of PET/MR imaging with that of FDG PET/CT and to determine the MR sequences necessary for the detection of liver metastasis using a trimodality PET/CT/MR set-up. METHODS: Included in this single-centre IRB-approved study were 55 patients (22 women, age 61 ± 11 years) with suspected liver metastases from gastrointestinal cancer. Imaging using a trimodality PET/CT/MR set-up (time-of-flight PET/CT and 3-T whole-body MR imager) comprised PET, low-dose CT, contrast-enhanced (CE) CT of the abdomen, and MR with T1-W/T2-W, diffusion-weighted (DWI), and dynamic CE imaging. Two readers evaluated the following image sets for liver metastasis: PET/CT (set A), PET/CECT (B), PET/MR including T1-W/T2-W (C), T1-W/T2-W with either DWI (D) or CE imaging (E), and a combination (F). The accuracy of each image set was determined by receiver-operating characteristic analysis using image set B as the standard of reference. RESULTS: Of 120 liver lesions in 21/55 patients (38 %), 79 (66 %) were considered malignant, and 63/79 (80 %) showed abnormal FDG uptake. Accuracies were 0.937 (95 % CI 89.5 - 97.9 %) for image set A, 1.00 (95 % CI 99.9 - 100.0 %) for set C, 0.998 (95 % CI 99.4 - 100.0 %) for set D, 0.997 (95 % CI 99.3 - 100.0 %) for set E, and 0.995 (95 % CI 99.0 - 100.0 %) for set F. Differences were significant for image sets D - F (P < 0.05) when including lesions without abnormal FDG uptake. As shown by follow-up imaging after 50 - 177 days, the use of image sets D and both sets E and F led to the detection of metastases in one and three patients, respectively, and further metastases in the contralateral lobe in two patients negative on PET/CECT (P = 0.06). CONCLUSION: PET/MR imaging with T1-W/T2-W sequences results in similar diagnostic accuracy for the detection of liver metastases to PET/CECT. To significantly improve the characterization of liver lesions, we recommend the use of dynamic CE imaging sequences. PET/MR imaging has a diagnostic impact on clinical decision making

Dynamic pelvic floor imaging: MRI techniques and imaging parameters

Magnetic resonance imaging (MRI) is an excellent tool to understand the complex anatomy of the pelvic floor and to assess pelvic floor disorders. MRI enables static and dynamic imaging of the pelvic floor. Using static T2-weighted sequences the morphology of the pelvic floor can be visualized in great detail. A rapid half-Fourier T2-weighted, balanced steady state free precession, or gradient-recalled echo sequence are used to obtain sagittal images while the patient is at rest, during pelvic squeeze, during pelvic strain and to document the evacuation process. On these images the radiologist identifies the pubococcygeal line (PCL) (which represents the level of the pelvic floor). In normal findings, the base of the anterior and the middle compartment are above the PCL at rest, and the pelvic floor elevates during contraction. During straining the pelvic floor muscles should relax and the pelvic floor descends normally less than 3 cm below the PCL. Pelvic floor MRI based on the static and dynamic MRI sequences allows for the detection and characterization of a vast array of morphologic and functional pelvic floor disorders. In this review, we focus on technical aspects of static and dynamic pelvic floor MRI

Intravoxel incoherent motion analysis of abdominal organs: application of simultaneous multislice acquisition

PURPOSE: The aim of this study was to systematically evaluate the accuracy of quantitative intravoxel incoherent motion (IVIM) analysis of the upper abdomen applying simultaneous multislice (SMS) diffusion-weighted imaging (DWI) to reduce acquisition time. MATERIALS AND METHODS: Diffusion-weighted imaging of parenchymal abdominal organs was performed in 8 healthy volunteers at 3 T using a standard DWI sequence (acceleration factor 1 [AF1]) and an SMS-accelerated echo planar imaging sequence with acceleration factors 2 and 3 (AF2/AF3). Intravoxel incoherent motion analysis was performed with a multistep algorithm for true diffusion coefficient (Dt), pseudodiffusion coefficient (D*), and fraction of perfusion (Fp) measured for the liver, kidney cortex and medulla, pancreas, spleen, and erector spinae muscle. Qualitative and quantitative parameters were compared using a repeated measurement 1-way analysis of variance test and the Bonferroni post hoc method. RESULTS: Simultaneous multislice DWI provided diagnostic image quality in all volunteers with a reduction of scan time of 50% for AF2 (67% for AF3) compared with the standard sequence. Decent IVIM analysis for Dt, D*, and Fp can be calculated on the images of both the SMS sequences AF2 and AF3 with typical organ characteristics of IVIM; however, systematical deviations from AF1 were observed: Dt values increased and Fp decreased significantly with higher acceleration factor for liver, kidney, pancreas, and muscle (P < 0.05). Fitting curves of higher acceleration factors tend to be more monoexponentially shaped. CONCLUSIONS: Simultaneous multislice acceleration provides considerable scan time reduction for upper abdomen DWI with equivalent quality of IVIM analysis compared with the standard nonaccelerated technique. Systematic discrepancies of the true Dt, D*, and Fp for SMS acquisitions need to be considered when comparing to standard DWI sequences

Liver-fat and liver-function indices derived from Gd-EOB-DTPA-enhanced liver MRI for prediction of future liver remnant growth after portal vein occlusion

OBJECTIVES To evaluate the use of Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI)-derived fat- and liver function-measurements for prediction of future liver remnant (FLR) growth after portal vein occlusion (PVO) in patients scheduled for major liver resection. METHODS Forty-five patients (age, 59 ± 13.9 y) who underwent Gd-EOB-DTPA-enhanced liver MRI within 24 ± 18 days prior to PVO were included in this study. Fat-Signal-Fraction (FSF), relative liver enhancement (RLE) and corrected liver-to-spleen ratio (corrLSR) of the FLR were calculated from in- and out-of-phase (n=42) as well as from unenhanced T1-weighted, and hepatocyte-phase images (n=35), respectively. Kinetic growth rate (KGR, volume increase/week) of the FLR after PVO was the primary endpoint. Receiver operating characteristics analysis was used to determine cutoff values for prediction of impaired FLR-growth. RESULTS FSF (%) showed significant inverse correlation with KGR (r=-0.41, p=0.008), whereas no significant correlation was found with RLE and corrLSR. FSF was significantly higher in patients with impaired FLR-growth than in those with normal growth (%FSF, 8.1 ± 9.3 vs. 3.0 ± 5.9, p=0.02). ROC-analysis revealed a cutoff-FSF of 4.9% for identification of patients with impaired FLR-growth with a specificity of 82% and sensitivity of 47% (AUC 0.71 [95%CI:0.54-0.87]). Patients with impaired FLR-growth according to the FSF-cutoff showed a tendency towards higher postoperative complication rates (posthepatectomy liver failure in 50% vs. 19%). CONCLUSIONS Liver fat-content, but not liver function derived from Gd-EOB-DTPA-enhanced MRI is a predictor of FLR-growth after PVO. Thus, liver MRI could help in identifying patients at risk for insufficient FLR-growth, who may need re-evaluation of the therapeutic strategy

Quantitative perfusion analysis of malignant liver tumors: Dynamic computed tomography and contrast-enhanced ultrasound

OBJECTIVE:: To prospectively analyze the correlation between quantitative parameters of perfusion derived from dynamic contrast-enhanced CT (DCE-CT) and contrast-enhanced ultrasound (DCE-US) in patients with malignant liver tumors. MATERIALS AND METHODS:: Thirty patients (mean age: 59.4 ± 12.3 years) with primary malignant liver tumors or hepatic metastases of various origin underwent DCE-CT (4D spiral mode, scan range, 14.8 cm; 15 scans; cycle time, 3 seconds) and DCE-US (low mechanical index, <0.1, 2.4 mL microbubbles). DCE-CT and DCE-US images were evaluated by 2 radiologists regarding quantitative perfusion parameters including arterial liver perfusion (ALP), portal-venous perfusion (PVP), and total perfusion (P = ALP + PVP) from DCE-CT, as well as blood inflow velocity (B) and the normalized slope within the calculation range (CVan) from DCE-US. RESULTS:: Quantitative assessment was possible with DCE-CT in 12/30 (40%) patients before and in all patients after automated motion correction. With DCE-US, quantitative assessment could not be performed in 9/30 (30.0%) patients due to respiratory motion. Interreader agreements for quantitative perfusion analysis were good with DCE-CT (r = 0.640-0.892, each P < 0.001) and DCE-US (r = 0.761-0.909, each P < 0.001). Moderate significant correlations were found between the perfusion parameters from DCE-CT (P, ALP) and DCE-US (B, CVan) (r = 0.446-0.621, each P < 0.05). No significant correlations were found between PVP from CT and perfusion parameters from DCE-US (B, CVan; each P = nonsignificant). CONCLUSIONS:: Quantitative evaluation of DCE-CT data was feasible in all patients after automated motion correction, whereas DCE-US data could not be quantitatively evaluated in 30% of patients due to respiratory motion and lack of motion correction software. Quantitative arterial perfusion analysis showed moderate significant correlations for blood flow parameters among modalities